BSMULT-Atmospheric band removal using a B star calibration spectrum

Description:

BSMULT applies the calibration spectrum derived from a B-star (for atmospheric bands) to the spectrum of an object.

Parameters:

SPECTRUM

The spectrum specified by SPECTRUM will be multiplied by the B star calibration spectrum (specified by BSTAR). BSMULT differs from a simple multiplication (e.g. IMULT) in taking account of the differences in air mass of the calib- ration object and the object being calibrated. So both should have valid values for .OBS.SECZ (the program will complain if they don't). Note that the calibration is by multiplication, and so is not suitable for data in logarithmic flux units such as magnitudes.

BSTAR

BSTAR specifies the B-star calibration spectrum, obtained by dividing a B star (or other suitable calibration spetrum) by its continuum. Any regions where no correction is desired should be set to 1.0.

OUTPUT

OUTPUT specifies the name of the calibrated spectrum to be produced by BSMULT. Note that this can be the same as for SPECTRUM, in which case the operation will be performed in situ.

BETA

The algorithm used by BSMULT is:

OUTPUT=SPECTRUM*(BSTAR**(SSECZ/BSECZ)**BETA))

where SSECZ and BSECZ are the air masses for the spectrum and the B star respectively. BETA should be 0.5 for saturated lines, 1.0 for unsaturated lines, and the generally accepted best compromise value for all lines (determined by P.J. Young) is 0.55.

Source comments:

 B S M U L T

 Multiplies a spectrum by a B star calibration spectrum - which
 should be 1.0 except in regions where there are atmospheric
 bands.  This routine differs from an ordinary multiplication (e.g.
 as in IMULT) since it includes a term for the correction due
 to the different air masses of the two objects.  This means
 that both the original spectrum and the B star spectrum must
 have valid .OBS.SECZ values.  If the spectrum to be multiplied
 is 2 dimensional, the same operation is repeated for each of
 the spectra it contains.

 Command parameters -

 SPECTRUM    (Character) The spectrum to be corrected.
 BSTAR       (Character) The B star calibration spectrum.
 BETA        (Numeric) Power to which relative air mass is
             to be raised - see FIG_BSMULT.
 OUTPUT      (Character) The resulting spectrum.

 Command keywords - None

 User variables used - None

                                     KS / CIT 3rd July 1984